Okenite Ca5si9o23² 9H2O

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Okenite Ca5Si9O23 ² 9H2O c 2001 Mineral Data Publishing, version 1.2 ° Crystal Data: Triclinic. Point Group: 1: As bladed crystals or laths, typically ¯brous with [010] as ¯ber axis. In aggregates of curved crystals, and compact radial ¯brous balls, to 4 cm. Twinning: About [010], composition plane 102 , lamellar. f g Physical Properties: Cleavage: Perfect on 001 . Tenacity: Elastic. Hardness = .5{5 f g D(meas.) = 2.28{2.33 D(calc.) = 2.33 Optical Properties: Transparent to translucent. Color: White, slightly yellow; in thin section, colorless. Luster: Vitreous to pearly. Optical Class: Biaxial ({). ® = 1.530 ¯ = 1.536 ° = 1.541{1.553 2V(meas.) = Large. Cell Data: Space Group: P 1: a = 9.69(1) b = 7.28(1) c = 22.02(4) ® = 92:7(2)± ¯ = 100:1(3)± ° = 110:9(1)± Z = [2] X-ray Powder Pattern: Bombay, India. 21 (vvs), 8.8 (vs), 3.56 (vs), 2.93 (vs), 3.07 (s), 3.05 (s), 2.98 (ms) Chemistry: (1) (2) SiO2 53.88 55.00 Al2O3 0.08 Fe2O3 0.01 CaO 27.61 28.51 SrO 0.27 Na2O 0.12 K2O 0.06 H2O 18.02 16.49 Total 100.05 100.00 (1) Bombay, India. (2) Ca5Si9O23 ² 9H2O: Occurrence: Commonly in amygdules in basalts. Association: Zeolites, apophyllite, prehnite, calcite, quartz, \chalcedony." Distribution: From Greenland, at Qutdligssat (Kudlisat), Ritenbenk district; on Quqertarsuaq [Disko] Island, at Skarvefjeld and Bl½sedal, Godhavn district; and elsewhere. On Bordoy and Streymoy, Faeroe Islands. At Scawt Hill, near Larne, Co. Antrim, Ireland. On the Isle of Mull and on Morven Peak, Grampian Highlands, Scotland. In India, in Maharashtra, from the Syhadree Mountains; the Bombay quarry, Bombay; around Poona; and in the Nasik and Kolhapur districts. At Rio Putagan, Chile. In the Noche Buena mine, Mazapil, Zacatecas, Mexico. In the USA, at Crestmore, Riverside Co., California; in the Fairfax quarry, Centreville, Fairfax Co., Virginia; and at Skookumchuck Dam, near Bucoda, Thurston Co., Washington. In the Je®rey mine, Asbestos, Quebec, Canada. Other localities are known. Name: For the German naturalist Lorenz Ocken (1779{1851), of Munich, Germany, the mineral name later shortened. References: (1) Dana, E.S. (1892) Dana's system of mineralogy, (6th edition), 565. (2) Gard, J.A. and H.F.W. Taylor (1956) Okenite and nekoite (a new mineral). Mineral. Mag., 31, 5{20. (3) Heller, L. and H.F.W. Taylor (1956) Crystallographic data for the calcium silicates. H.M. Stationary O±ce, London, 22{24. (4) Merlino, S. (1983) Okenite, Ca10Si18O46 ² 18H2O: the ¯rst example of a chain and sheet silicate. Amer. Mineral., 68, 614{622. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior written permission of Mineral Data Publishing..

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I`mt`qx1/00Lhmdq`knesgdLnmsg9Rbnkdbhsd This month’s mineral, scolecite, is an uncommon zeolite from India. Our write-up explains its origin as a secondary mineral in volcanic host rocks, the difficulty of collecting this fragile mineral, the unusual properties of the zeolite-group minerals, and why mineralogists recently revised the system of zeolite classification and nomenclature. OVERVIEW PHYSICAL PROPERTIES Chemistry: Ca(Al2Si3O10)A3H2O Hydrous Calcium Aluminum Silicate (Hydrous Calcium Aluminosilicate), usually containing some potassium and sodium. Class: Silicates Subclass: Tectosilicates Group: Zeolites Crystal System: Monoclinic Crystal Habits: Usually as radiating sprays or clusters of thin, acicular crystals or Hairlike fibers; crystals are often flattened with tetragonal cross sections, lengthwise striations, and slanted terminations; also massive and fibrous. Twinning common. Color: Usually colorless, white, gray; rarely brown, pink, or yellow. Luster: Vitreous to silky Transparency: Transparent to translucent Streak: White Cleavage: Perfect in one direction Fracture: Uneven, brittle Hardness: 5.0-5.5 Specific Gravity: 2.16-2.40 (average 2.25) Figure 1. Scolecite. Luminescence: Often fluoresces yellow or brown in ultraviolet light. Refractive Index: 1.507-1.521 Distinctive Features and Tests: Best field-identification marks are acicular crystal habit; vitreous-to-silky luster; very low density; and association with other zeolite-group minerals, especially the closely- related minerals natrolite [Na2(Al2Si3O10)A2H2O] and mesolite [Na2Ca2(Al6Si9O30)A8H2O]. Laboratory tests are often needed to distinguish scolecite from other zeolite minerals. Dana Classification Number: 77.1.5.5 NAME The name “scolecite,” pronounced SKO-leh-site, is derived from the German Skolezit, which comes from the Greek sklx, meaning “worm,” an allusion to the tendency of its acicular crystals to curl when heated and dehydrated.
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